Sapporo Beer Museum  ; besides the free short self-tour, after that at the eating hall, can buy 3 glasses of Classic, Black Label & Kaitakushi at slight discount .... unless you can't consume alcohol lah.

Can skip Hokkaido Museum (further from Sapporo city centre), relatively nothing much to see for ¥600; but Hokkaido University Museum (nearer) got more things to see, for free ... (got nice milk ice-cream at the university museum cafe).

Eating ... Nijo market ... had my best salmon sashimi (so far in my life, I feel) there (supposedly was Premilum Summer Salmon  , dunno autumn/winter got the same salmon or not)  [attachmentid=10352699]
If you like shiroi koibito cookies, then maybe Ishiya Chocolate Factory is a must.

Sight-seeing ... the usual around city centre okay attractions such as Odori Park, Sapporo TV Tower, Clock Tower, Former Hokkaidō Government Office ... those instagrammable places.

December ... not yet Sapporo Snow Festival ... too bad.

Otaru ... main attraction is the canal ... seafood, ya, maybe Sapporo can get the same quality (Nemuro on the other hand, seems fresher, maybe placebo thinking ... but that's too far away) ... I guess if you're a fan of the movie "Love Letter (1995)", maybe it's another must.